This invention relates to panic exit devices having one or more vertically operating bolts at the top and/or bottom of the door. An example of such a device wherein the bolts may be retracted solely by means of a key operated lock which also services to lock the bolts in the retracted position or by depressing a panic bar, is described in the United States Patent to T. Bejarano, U.S. Pat. No. 3,334,500.
There are numerous types and styles of mechanisms used for operating the popular commercial and industrial door latch where the bolts reciprocate vertically and extend from the top and bottom of the door. Most of these mechanims include or are adapted to include a panic bar release arrangement on the inside of the door for rapid and foolproof actuating of the bolts by merely depressing the panic bar to open the door. Many such mechanisms include an often desirable feature of permitting manipulation of a device to latch the bolts in a retracted position during business hours or the like, whereby the door is free to swing open without operating the panic bar or hitting any other release mechanism. This is known in the industry as a "dogging" feature and is usually accomplished by flipping a lever or threading a screw into a position to block the operating mechanism in the depressed position of the panic bar or other release mechanism. Often, it is particularly desirable that this dogged condition of the door not be inadvertantly or maliciously released and therefore, a special tool or unique knowledge might be required to set and release the dogging mechanism. For example, a recessed screw has been used as the actuating means for the dogging mechanism whereby a screwdriver and considerable effort are needed for actuation, but this has the inherent objectionable feature of requiring a substantial amount of the authorized operator's time to actuate the dogging mechanism. Another now-conventional arrangement as shown in the aforementioned U.S. Pat. No. 3,334,500 provides a pivotable stud having a relieved shank portion adapted to engage a portion of the bolt retraction mechanism so as to reach a dogged condition with a 1/2 turn rotation of the stud. Although this dogging arrangement is an improvement over other methods, it results in the tension being removed from the panic bar handle, leaving it in a flopable condition.
Another feature that is often required with this type of bolt mechanism is the provision of a keyed exterior lock to permit opening of the door from the outside. Conventionally, these mechanisms are provided with an exterior lever or knob which is released by the operation of the keyed lock and then may be manipulated to retract the bolts for opening the door. Alternatively, the keyed lock may operate a separate bolt which must be released before the door may be opened by the operation of the knob or lever. U.S. Pat. No. 3,334,500 provides a vertical bolt operating mechanism capable of actuation by an exterior keyed lock, wherein the bolts may be latched in their retracted position by appropriate manipulation of the keyed lock in conjunction with manipulation of an interiorly facing operating means, and that arrangement is particularly suitable for and compatible with the present invention.
Still another desirable feature in many installations of this type of bolt mechanism is to minimize the size of both the door stile containing the bolts and the mechanism for operating the bolts. This is particularly desirable with glass doors which derive their esthetic quality from their uncluttered look. The particular locking mechanism disclosed by Bejarano allows such a narrow door stile. Additionally, it is desirable to provide an exit device which may be easily and economically mounted on the door stile, regardless of whether the bolt mechanism is on the left hand or right hand stile.
To provide smooth operation of installations of this type, some form of bolt latching mechanism is usually provided which retains the bolts in the retracted position when the interior or exterior actuating device is operated during the time the door is open. This prevents the need to continue pressure on the panic bar or key in order to prevent the bolt from contacting the ground while the door is swinging open and closed. The bolt latching mechanism is usually designed to trip and release the bolt when the door reaches the closed position. U.S. Pat. No. 3,334,500 shows such a latching mechanism. However, latching mechanisms of this type have proved unsatisfactory, since the bolt which is screwed on the connecting shaft must be rotated a full 360.degree. in order to vary the portion of the bolt which extends above and below the door. This often results in situations where one turn more is too much, but the present length is not enough. Therefore, it would be desirable to provide a bolt latching mechanism which allows more flexability in adjusting the length of the bolt extending above or below the door.